Is going from McIntosh C712 to C46 worth it?

With an MC2102, I think you would find the C50 to be a major improvement over the C712 and especially if you are into vinyl.  The tone controls are excellent and the design is outstanding.  The built-in DAC goes up to 32 bit / 192 kHz PCM and all of the inputs are adjustable for trim.  A very nice rig that should beautifully compliment your amp and speakers.  My 2 cents, anyway.

Good luck and happy listening!